escape sequences

The backslash character \ is used to escape single byte character codes or Unicode entry points.

The form \ooo (where ooo is a 3 character octal value) can be used to index a known character code in a specific font encoding. For example the Adobe Symbol font uses a custom encoding in which octal 245 represents the infinity symbol. You could embed this in an enhanced text string by giving the font name and the character code "{/Symbol \245}". This is mostly useful for the PostScript terminal, which cannot easily handle UTF-8 encoding.

You can specify a character by its Unicode code point as \U+hhhh, where hhhh is the 4 or 5 character hexadecimal code point. For example the code point for the infinity symbol is \U+221E. This will be converted to a UTF-8 byte sequence on output if appropriate. In a UTF-8 environment this mechanism is not needed for printable special characters since they are handled in a text string like any other character. However it is useful for combining forms or supplemental diacritical marks (e.g. an arrow over a letter to represent a vector). See set encoding, utf8, and the online unicode demo.